my country's sanitation industry started late, and there is no monitoring method for total chromium in urban domestic waste in China. The monitoring method of soil is generally used, but the characteristics of soil and domestic waste are different. In order to standardize the determination method of total chromium in urban domestic waste, this standard is specially formulated. This standard specifies the principle, main instruments, reagents and operating procedures for the determination of total chromium content by diphenylcarbazide colorimetry. This standard is applicable to the determination of total chromium in urban domestic waste. CJ/T 97-1999 Determination of total chromium in urban domestic waste Diphenylcarbazide colorimetry CJ/T97-1999 Standard download decompression password: www.bzxz.net

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Town construction industry standard of the People's Republic of China CJ/T97—1999
Municipal domestic refuse
Determination of total chromium
Diphenylcarbazide color method
Municipal domestic refuse-Determination of total chromium-Diphenylcarbazide color methodConstruction standard
1999-11-24Promulgated
2000-06-01Implementation
Ministry of Construction of the People's Republic of China
Engineering construction standard full text information system
Engineering construction standard full text information system
CJ/T97-1999
my country's environmental sanitation industry started late, and there is a blank in the country for monitoring methods of total chromium in municipal domestic waste. The monitoring methods of soil are generally used for reference, but the characteristics of soil and domestic waste are different. This standard is formulated to standardize the determination method of total chromium in urban domestic waste.
This standard is proposed by the Standard and Quota Research Institute of the Ministry of Construction. This standard is managed by the Shanghai Municipal Environmental Sanitation Administration, the technical management unit of urban environmental sanitation standards of the Ministry of Construction.
This standard was drafted by the Tianjin Environmental Sanitation Engineering Design Institute. The main drafters of this standard are Yao Qingjun and Zhang Fan. This standard is entrusted to the Tianjin Environmental Sanitation Engineering Design Institute for interpretation. Engineering Construction Standard Full-text Information System
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Standard of Urban Construction Industry of the People's Republic of China Determination of total chromium
Municipal domestic refuse
Diphenyl carbazide colorimetric method
Municipal domestic refuse-Determination of total chromium-Diphenyl carbazide color methodScope
CJ/T97—1999
This standard specifies the principle, main instruments, reagents and operating procedures for the determination of total chromium content by diphenyl carbazide colorimetric method.
This standard is applicable to the determination of total chromium in municipal domestic refuse. 2 Referenced Standards
The provisions contained in the following standards constitute the provisions of this standard through reference in this standard. When this standard is published, the versions shown are valid. All standards will be revised, and parties using this standard should explore the possibility of using the latest versions of the following standards. CJ/T3039-1995 Sampling and physical analysis methods for municipal solid waste Sample collection and preparation
The collection and preparation of municipal solid waste samples, the determination of moisture content and the preservation of samples shall be carried out in accordance with the provisions of CJ/T3039. 4 Principle
After the sample is digested with sulfuric acid and nitric acid, the chromium-containing compounds become soluble, and the trivalent chromium is oxidized to hexavalent chromium with potassium permanganate solution, and the excess potassium permanganate in the digestion solution is decomposed with sodium azide solution. Approved by the Ministry of Construction of the People's Republic of China on November 24, 1999 Engineering Construction Standard Full Text Information System
Implementation on June 1, 2000
Engineering Construction Standard Full Text Information System
Under acidic conditions, hexavalent chromium reacts with diphenylcarbohydrazide to form a purple-red compound, and the absorbance is measured at a wavelength of 540nm. 5 Reagents
Unless otherwise specified, the reagents used in this standard are analytically pure reagents and distilled water that meet national standards.
5.1 Concentrated sulfuric acid (H,SO,), p=1.84g/mL. 5.2 Concentrated phosphoric acid (HPO,), p=1.69g/mL. 5.3 Concentrated nitric acid (HNOg), p=1.40g/mL. 5.4 0.5% potassium permanganate (KMmO,) solution (m/V). 5.5 0.5% sodium azide (NaN) solution (m/V). 5.6 0.25% diphenylcarbohydrazide acetone solution: Weigh 0.25g diphenylcarbohydrazide (CsHN,O) and dissolve it in acetone (CHCOCHg), and dilute it to 100mL with acetone. Prepare it when using.
5.7 Phosphoric acid solution, 1+1 (V/V): Heat the prepared solution to boiling, and while hot, drop the dilute potassium permanganate solution until it turns slightly red.
5.85% sulfuric acid-phosphoric acid mixture: Take 5 mL of concentrated sulfuric acid and concentrated phosphoric acid, slowly pour into water, and dilute to 100 mL. Heat the mixture to boiling and quickly add dilute potassium permanganate solution until it turns slightly red.
5.9 Chromium standard stock solution: Accurately weigh 0.2829 g potassium dichromate (K, Cr07, high-grade purity, and baked at 105110℃ for 2h) and dissolve in water, then transfer to a 1000 mL volumetric flask and dilute to the mark. The chromium concentration of this solution is 100μg/mL. 5.10 Chromium standard working solution: Accurately pipette 1.00 mL of chromium standard stock solution (5.9) into a 100 mL volumetric flask and dilute to the mark. The chromium concentration of this solution is 1.0ug/mL. 6 Instruments
a) Spectrophotometer;
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b) Electric hot plate;
c) Analytical balance;
d) 25mL stoppered colorimetric tube.
7 Operating steps
7.1 Drawing of standard curve
7.1.1 Preparation of standard working solution
Put 0.00, 0.50, 1.00, 2.00, 3.00, 4.00, 5.00, 8.00, 10.00mL of chromium standard working solution (5.10) in 25mL colorimetric tubes, add 2.5mL of sulfuric acid-phosphoric acid mixture (5.8), then add 2mL of phosphoric acid solution (5.7), shake well, and dilute with water to the mark. Prepare a series of standards of 0.00, 0.50, 1.00, 2.00, 3.00, 4.00, 5.00, 8.00, and 10.00 g of chromium.
7.1.2 Color development and determination
Add 2 mL of diphenylcarbazide acetone solution (5.6) to each colorimetric tube (7.1.1), shake well quickly, and let stand for 10 minutes. Adjust the instrument to the best working conditions according to the instrument manual, use a 3 cm colorimetric dish, and use the reagent blank (zero concentration) as a reference to measure the absorbance at a wavelength of 540 nm.
7.1.3 Draw a standard curve
Draw a standard curve with the absorbance of the standard solution as the ordinate and the corresponding chromium content of the standard solution as the abscissa.
7.2 Determination of sample
7.2.1 Sample pretreatment
Weigh about 0.5g of sample, accurate to 0.0001g, and place it in a 150mL conical flask. After wetting the sample with a little water, add 3.0mL each of sulfuric acid (5.1), phosphoric acid (5.2), and nitric acid (5.3) and shake well. Cover with a small funnel and soak overnight. Then place on a hot plate and heat to digest (temperature controlled below 200℃) until white smoke comes out. If the sample still does not turn white, remove the conical flask and cool it slightly, then repeat adding 1.0~1.5mL of nitric acid (5.3) solution, and heat until a lot of white smoke comes out, the sample turns white, and the digestion solution turns light yellow-green. 3
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Remove the conical flask, rinse the small funnel and the flask wall with water, transfer all the digestion solution and residue into a 100mL volumetric flask, add water to the mark, shake and let it stand, and retain the supernatant A for the determination of (7.2.2).
7.2.2 Determination
Pull 10.00mL of the supernatant A obtained in (7.2.1) into a 25mL colorimetric tube, add 2.0mL of phosphoric acid solution (5.7), and drop 1~2 drops of potassium permanganate solution (5.4) until the test solution turns purple-red. Place the colorimetric tube in a water bath and heat and boil for 15 minutes. If the purple-red color fades, add another drop of potassium permanganate solution (5.4). Add sodium azide solution (5.5) while it is hot and shake continuously until the purple-red color fades. Immediately put it in cold water, add water to the mark after cooling, and shake well. The following steps are the same as (7.1.2). 7.3 Blank experiment
Blank experiment is carried out simultaneously with sample determination. Except for not adding sample, the reagents and their dosages are the same as those for sample determination.
Expression of analysis results
The content of chromium c (mg/kg) is calculated as follows: mVrelease
c=Vmsample
Where: c—concentration of sample, mg/kg; m
the amount of chromium in the sample found on the standard curve, omitted; Vsample—volume of sample fixed volume, mL;
V—volume of sample solution taken during determination, mL; msample—weight of weighed sample, 8.
The result should be expressed to four decimal places.
9 Precision and Accuracy
Two samples were measured in the laboratory, and four parallel samples were made for each sample. A total of four batches of experiments were conducted. The total chromium content was 34.2~61.8mg/kg, and the relative standard deviation was 4
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1.5%~5.7%. When 10~20g of standard chromium was added to 0.5g of sample, the recovery rate was 92.5%~98.2%.
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